1. Field of the Invention
The present invention relates to the preparation of methylated tertiary amines, and, more especially, to the preparation of methylated tertiary amines by reacting hexamethylenetetramine with certain nitrogen compounds in the presence of hydrogen and a hydrogenation catalyst.
The monomethylated or dimethylated tertiary amines which can be prepared according to the present invention constitute a wide variety of cyclic and acyclic amines having, inter alia, the following general formulae: ##STR1## These also comprise the polyamines and mixed amines and polyamines.
2. Description of the Prior Art
The mono- or dimethylated tertiary amines comprise at least three types of compounds that are extensively researched in industry, e.g., quaternary ammonium salts, betaines and amine oxides, which find numerous applications in detergents, cosmetics, as bactericides, antibiotics, as agents for treating textiles, or for making organophilic clays.
Numerous processes are known to this art for preparing methylated tertiary amines, for example the direct methylation of primary or secondary amines by means of various methylation reagents such as methyl chloride or sulfate, or by the formaldehyde/formic acid system (Leuckart-Wallach reaction; see Merck Index, 1Oth Edition, p. ONR-55), by the hydrogenation of dialkylamides (EP-412,359 (Hoechst) or FR-2,633,927 (CECA S.A.)), or by the transformation of nitriles by the formaldehyde/hydrogen system (JP-63/287,752 (Kao Soap)).
These processes, however, present various major disadvantages. For example, those which are based on the Leuckart reaction, which itself is difficult to conduct, produce amines which are contaminated, inter alia, by formaldehyde; others, which entail methylation by methyl chloride, in addition to generating hydrochloric acid, lack selectivity and the resulting products contain quaternary ammonium salts in proportions that are difficult to control. The direct hydrogenation of amides uses a copper chromite catalyst, which is incompatible with the nickel catalyst otherwise employed in plants for preparing amines, and this multiplies the number of processing units required and increases the total cost of production of these plants.